Secretary of State John F. Kerry met Tuesday morning with several of the diplomats who signed an internal memo urging the United States to use more military force in Syria to compel the government to abide by a truce and negotiate a political solution.

A senior State Department official, speaking on the condition of anonymity about the private conversation, said Kerry met for 30 minutes with 10 of the memo’s 51 signatories. The official declined to discuss the substance of their conversation.

The memo, marked “Sensitive But Unclassified,” was posted last week on an official “dissent channel” established during the Vietnam War for employees to voice their concerns without fear of repercussions. The signatories were all mid-level diplomats who have worked on Syrian policy issues over the past five years since peaceful protests against the government mushroomed into a civil war. The fighting in Syria has left more than 400,000 people dead, displaced more than half the population, and created a wave of refugees in neighboring countries and Europe.

Memos are sent to the dissent channel every year, and they are typically written by individuals or small groups of diplomats. The large number of signatories to this memo reflects a growing frustration within the State Department over continued ceasefire violations, the Syrian government’s blocking of humanitarian aid convoys, and the ongoing violence and suffering.

Although U.N.-brokered talks between the government and the opposition started earlier this year, they are on hold. The United States is leading coalitions of countries that are trying to get the talks back on track, and conducting a military campaign against the Islamic State that has carved out a caliphate in Syria and Iraq.

The 10-point memo that the diplomats submitted argues that the Russian and Iranian military support of the Syrian government of Bashar al-Assad weakens the potential for an enduring ceasefire and negotiations.

“Initiating targeted military strikes in response to egregious regime violations of the [cessation of hostilities] would raise the cost for the regime and bolster the prospects for a real ceasefire – without cities being bombed and humanitarian convoys blocked – and lead to a more serious diplomatic process, led by the United States,” the memo stated.

The memo contends that a “more muscular military posture under U.S. leadership” would assert the willingness to impose “consequences” on the Assad government, and increase U.S. negotiating leverage.

“We are not advocating for a slippery slope that ends in a military confrontation with Russia,” the memo said. “Rather, we are calling for a credible threat of targeted U.S. military responses” to enforce a truce and negotiations.